The invention is to be considered in conjunction with U.S. Pat. No. 4,899,666, Meier, which shows a modular conveying system, whose tracks have correspondingly constructed chain guidance channels with push and pull operable conveying chains without a return strand moving therein. Each of the end regions of said chains is provided with a conveying means for receiving a load and for moving the same on the associated track and the other of which its guided in each case by a correspondingly constructed drive member and can be moved backwards and forwards by the same. The aforementioned discloses among other things a switch or deflector, by means of which different portions of the conveying system can be interconnected in a selectable manner.
This switch comprises a planar, circular plate, which is located in the centre of a track branch and is provided with one or more portions of chain guidance channels. Through the rotation of this plate, which to a certain extent forms a local traffic junction, one or other portion can be positioned in such a way that it links the chain channel of an entering track with the chain channel of an exiting track located on the other side of the plate.
This makes it possible in a simple efficient manner to in particular obtain Y-shaped branches. Although with such a rotary plate it is fundamentally possible to control simple crossings as well as branches, limits are relatively rapidly reached with the increasing degree of complexity of the junction and it is not possible to pass beyond these with the aforementioned concept. This will be illustrated hereinafter.
Such a switch fundamentally has two functions, namely a positive function, i.e. the random connection of two facing tracks, and a negative function, namely the interruption of the other possible connections, the latter being for traffic safety purposes. In other words, whilst one portion of the switch forms a connection between chain guidance channels of two facing tracks, it must be ensured that simultaneously another portion of the switch is not coinciding with the chain guidance channel of another track. In practice this means that as a result of the finite dimensions and minimum radii of curvature of the tracks, such a switch only permits a restricted number of potential connections.
The number of potential connections (the degree) of a junction is the product of the number of entrances and exits, said two terms being fundamentally interchangeable here and merely refer to facing tracks or roads. In practice, the aforementioned planar rotary plate makes it possible to produce junctions up to the fourth degree. Thus, a second degree junction corresponds to the aforementioned Y-branch with two entrances and one exit, whilst a fourth degree junction corresponds to a branch with two entrances and two exits. Even if possible, higher degrees would be difficult to achieve, because with the increasing number of tracks to be connected there is a rise in the number of channel portions to be provided on the plate. Bearing in mind the traffic safety principle, there must be no crossings of individual portions on the actual plate and all tracks not participating in the actual connection must be blocked by the switch.